A variety of useful high performance polymers, or so-called engineering resins, are prepared by polymerizing various polymerizable carboxy-substituted arylene compounds. Accordingly, there exists considerable interest in commercially practical, efficient synthetic methods which can be used to prepare such compounds from low cost starting materials. Heretofore known methods are generally inefficient and/or excessively costly.
For example, isopropylidene bis(phthalic acid) (IBPA), also known as 2,2-bis(3,4-dicarboxyphenyl) propane, and its anhydride, isopropylidene bis(phthalic anhydride) (IPAN), are polymerizable into polymers that are useful for blending with polyether ketone and polyimide resins. These particular compounds can be prepared by oxidizing 2,2-dixylyl propane, also known as isopropylidene bis(xylene) and as 2,2-bis-(3,4-dimethylphenyl) propane (DXP).
DXP can be prepared by a known method involving the Friedel-Crafts coupling of o-xylene with 2,2-dichloro propane, as disclosed in U.S. Pat. No. 2,712,543 to Gresham et al. ##STR1##
This reaction does produce about a 50 percent yield of DXP, but this route is impractical because of the prohibitive cost of 2,2-dichloro propane.
As another example, phenylindantricarboxylic acids, such as 1,3,3-trimethyl-6-carboxy-1-(3',4'-dicarboxyphenyl)indan, and its mixed acid anhydride, which are polymerizable into polymers useful for blending with polyether ketone and polyimide resins, can be prepared by oxidizing 1,3,3,6-tetramethyl-1-o-xylyl indan (TMXI).
No commercially practical synthetic route(s) or method(s) are known to the prior art for making commercial-scale quantities of TMXI.
A compound such as alpha-methyl styrene is available in commercial quantities and at a unit price which is not prohibitive. Alpha-methyl styrene can be reacted with hydrogen chloride to form the hydrochloride which in turn can be coupled with o-xylene to form 2-phenyl-2-xylyl propane (PXP). However, prior to the present invention, no commercially practical method was known by which 2-phenyl-2-xylyl propane could be converted into 2,2-dixylyl propane, so far as is now known.
Similarly, a compound such as alpha-4-dimethyl styrene is available in commercial quantities and at a unit price which is not prohibitive. Alpha-4-dimethyl styrene can be dimerized to produce 1,3,3,6-tetramethyl-1-p-tolyl indan. However, prior to the present invention, no commercially practical method was known by which 1,3,3,6-tetramethyl-1-p-tolyl indan could be converted into 1,3,3,6-tetramethyl-1-o-xylyl indan, so far as is now known.
Previously, it was reported [C. Serres and E. K. Fields, JACS, 88:4685 (1960)] that, in benzylation reactions catalyzed by aluminum chloride, the expected benzylation product is formed first and then undergoes transaralkylation (debenzylation and rebenzylation) with arene solvents. In addition, U.S. Pat. No. 3,043,886 teaches that a polyarylmethane can be reacted with an aromatic hydrocarbon (preferably the same aromatic hydrocarbon used to prepare the diarylmethane) in the presence of a Lewis acid to produce diaryl methanes. Also, it was reported by R. H. Allen et al., JACS, 81:42 (1958) that, in a solution of p-t-butyl toluene in o-xylene at 0.degree. C. having a weight ratio of 1:9 and containing aluminum chloride, the t-butyl group could be transferred to o-xylene without isomerizing p-t-butyl toluene. Olah et al, J. Org. Chem., 29:2310 (1964); 29:2313 (1964); and 29:1315 (1964); carried out Friedel-Crafts isomerizations of various substituted toluene and dialkylbenzenes, and demonstrated that isomerization in aromatic hydrocarbon solvents is entirely a dealkylation-realkylation process.
However, so far as now known, no one has previously transaralkylated a benzyl group in a diaryl-substituted lower alkane, such as a 2,2-diaryl propane, or in an aryl-substituted fused alkylene ring compound, such as a 1-aryl indan, to produce lower alkyl-substituted phenyl-substituted derivatives thereof. Such derivatives are suitable for oxidation to produce the corresponding carboxylated aryl alkanes and aryl carboxylated indan products.
A new and commercially practical method of preparing, for example, alkaryl-substituted propane-type compounds, such as 2,2-bis(lower alkyl-substituted phenyl) propanes, 1-(lower alkyl-substituted) phenyl indans, 2,2-bis(lower alkyl-substituted phenyl) methanes, and the like, from relatively low cost starting materials, would be economically advantageous. The present invention provides such a method.